Animal shock collar with low impedance transformer

ABSTRACT

A remote receiver unit is for use in an animal behavior modification system that applies an electrical shock to an animal. The remote receiver unit has an electrical shock device including two electrodes configured for contacting the animal, a source of alternating current voltage, and an electrical transformer with a primary coil and a secondary coil. The primary coil is electrically connected to the source of alternating current voltage. The secondary coil is electrically connected to at least one of the two electrodes. The transformer has an output impedance of less than 900 ohms. A receiver circuit is electrically connected to the shock device. The receiver circuit is configured for activating the shock device in response to a received signal.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 09/241,360, entitled “ANIMAL SHOCK COLLAR WITH LOWIMPEDANCE TRANSFORMER”, filed Jan. 29, 1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to animal behavior modificationsystems, and, more particularly, animal behavior modification systemswhich apply an electrical shock to an animal.

[0004] 2. Description of the Related Art

[0005] Animals such as dogs may be fitted with a collar which carries areceiver unit and a pair of electrodes for applying electricalstimulation to the skin of the dog in order to control its behavior. Forexample, a conventional pet containment system includes a stationarytransmitter which is connected to an endless wire placed around theconfinement area under the surface of the ground. Over the endless wire,the stationary transmitter transmits a radio frequency (RF) signal whichis received by the receiver unit if the dog approaches too close to thewire. In response to receiving the signal, a voltage is applied acrossthe electrodes, which causes an electrical current to flow through thedog's skin between the two electrodes. Alternatively, the trainer maycarry a portable transmitter which selectively transmits an RF signal tothe receiver unit for electrical stimulation when the animal exhibitsundesirable behavior. As another option, a stationary transmitter maytransmit an RF signal which is received by the receiver so long as thedog is in the confinement area. If the dog strays from the confinementarea, the RF signal is no longer received and electrical stimulation isapplied to the dog through the electrodes.

[0006] It is known to provide a voltage across the electrodes by using ahigh voltage, high output impedance flyback transformer with opencircuit voltages ranging between approximately 3000V and 10,000V at themaximum levels. The transformer is small enough to fit within theconfined housing on a collar placed around an animal's neck. In order togenerate the high voltage levels in a small package, the transformer hasnumerous turns of fine wire on the secondary coil and has an outputimpedance of greater than 1500 ohms.

[0007] A problem is that the electrodes can be at least partiallyshorted out or shunted by water between the electrodes. The water may becarried on the skin and/or fur of the dog, or the water may becompletely surrounding the electrodes when the dog is submerged inwater. This problem particularly occurs when the dog has been in therain, or when the dog goes into a lake, such as while hunting. The waterbetween the electrodes presents less electrical resistance(approximately 200-500 ohms) than does the dog's skin. Thus, most of thecurrent flows through the water, and the low level of remaining currentwhich flows through the dog's skin may not be enough to get the dog'sattention.

[0008] A related problem is that since the transformer's outputimpedance of over 1500 ohms is so much greater than the resistance ofthe water (200-500 ohms), there is both a large voltage drop across thesecondary coil and an impedance mismatch between the transformer and theload. The large voltage drop across the secondary coil reduces thevoltage that can be applied to the electrodes. The impedance mismatchlimits the amount of power that can be transmitted from the transformerto the load. In dry loading conditions, in which the electrodes arepressed against the animal's skin, the electroshock voltage levels dropto the hundreds of volts range, which is adequate to effect the desiredelectroshock stimulus. However, in water or in wet conditions, theelectroshock voltage levels drop to several tens of volts, which may becompletely undetectable by the animal.

[0009] It is also known to surround the sides of the electrodes with anelectrically insulating material which blocks the flow of currentthrough the adjacent water. Only the tips of the electrodes whichcontact the skin of the animal are left exposed. A problem is that theuninsulated electrode tips must be firmly pressed against and into theanimal's skin so that the skin effectively insulates the electrode tipsfrom the surrounding wet fur. However, pressing the electrode tipstightly against the animal's skin can lead to lesions and infections atthe electrode contact site. For this and other reasons, many dog ownersare reluctant to tighten the collar around the dog's neck to therequired degree.

[0010] Yet another problem is that internal arcing or corona dischargesmay occur within the receiver unit due to the transformer's high outputvoltage (up to 10,000V) when the system is unloaded. The close spacingbetween the electrical components or traces within the receiver unit, asrequired by the dimensional limitations of the receiver unit, increasesthe likelihood of such electrical arcing.

[0011] What is needed in the art is a dog training collar which providesan effective electroshock stimulus to either a dry or wet animal withoutinsulating the sides of the electrodes or burying the electrodes in theanimal's skin. Further, internal arcing due to the high voltages withinthe receiver unit must be avoided.

SUMMARY OF THE INVENTION

[0012] The present invention provides a dog training collar including alow impedance transformer which ensures that an adequate current issourced through the animal's skin, even in wet conditions. The opencircuit output voltage of the transformer is limited.

[0013] The invention comprises, in one form thereof, a remote receiverunit for use in an animal behavior modification system that applies anelectrical shock to an animal. The remote receiver unit has anelectrical shock device including two electrodes configured forcontacting the animal, a source of alternating current voltage, and anelectrical transformer with a primary coil and a secondary coil. Theprimary coil is electrically connected to the source of alternatingcurrent voltage. The secondary coil is electrically connected to atleast one of the two electrodes. The transformer has an output impedanceof less than 900 ohms. A receiver circuit is electrically connected tothe shock device. The receiver circuit is configured for activating theshock device in response to a received signal.

[0014] An advantage of the present invention is that an effectiveelectroshock stimulus can be applied to an animal in a wet environmentwithout insulating the electrodes and without the need for tighteningthe collar to such a degree that the electrodes are effectively buriedin the animal's skin.

[0015] Another advantage is that the open circuit output voltage of thetransformer is limited to thereby avoid internal arcing within thereceiver unit.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above-mentioned and other features and advantages of thisinvention, and the manner of attaining them, will become more apparentand the invention will be better understood by reference to thefollowing description of embodiments of the invention taken inconjunction with the accompanying drawings, wherein:

[0017]FIG. 1 is a perspective view of a transmitter and one embodimentof a receiver unit of the present invention; and

[0018]FIG. 2 is a schematic diagram of the receiver unit of FIG. 1.

[0019] Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate one preferred embodiment of the invention, in one form, andsuch exemplifications are not to be construed as limiting the scope ofthe invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Referring now to the drawings and particularly to FIG. 1, thereis shown an animal behavior modification system including a transmitter10 and an animal shock collar 12 carrying one embodiment of a remotereceiver unit 14 of the present invention. Remote receiver unit 14includes two probes or electrodes 16 and 18 projecting from ahermetically sealed box 20. Within box 20 is contained a receivercircuit 22 (FIG. 2) which receives a signal, indicated at 24,transmitted from transmitter 10. Remote receiver unit 14 also includesan electrical shock device 26 including a direct current (DC) powersupply 28, a charging capacitor 30, a transformer 32, a switching device34 and a transient voltage suppressor or voltage limiting device 36.

[0021] DC power supply 28 includes a battery having a positive terminal38 connected to transformer 32 and a grounded terminal 40. DC powersupply 28 can also have control circuitry (not shown) for receiving acontrol signal from receiver circuit 22 on line 42.

[0022] Transformer 32 includes a primary coil 44, having a firstterminal 46 connected to positive terminal 38 of battery 28, and asecond terminal 48 connected to switching device 34 and voltage limiter36. Transformer 32 also includes a secondary coil 50, having a thirdterminal 52 connected to electrode 16, and a grounded fourth terminal 54connected to electrode 18. Under operating conditions, the outputimpedance of transformer 32 can be less than 1000 ohms, and is typicallyless than 200 ohms.

[0023] By using a transformer with substantially less output impedancethan that of transformers known to be used in shock collars (over 1500ohms) the voltage drop across the secondary coil under wet conditions isgreatly reduced and, thus, more voltage can be applied to the electrodesunder wet, loaded conditions. Further, since the output impedance oftransformer 32 is closer to the resistance of the water surroundingelectrodes 16 and 18 (200-500 ohms), the problems associated with theimpedance mismatch between transformer 32 and the load are substantiallyreduced, thereby allowing more power to be transmitted throughelectrodes 16 and 18.

[0024] The turns ratio of transformer 32, i.e., the ratio of the numberof turns in secondary coil 50 to the number of turns in primary coil 44,can range approximately between 30 and 50. The inductance of secondarycoil 50 can range between approximately 0.05 H and 0.30 H, and morefavorably between approximately 0.10 H and 0.22 H. The resistance ofsecondary coil 50 can range approximately between 50 ohms and 900 ohms,and more favorably between 100 ohms and 150 ohms. The thickness of thewire forming secondary coil 50 can range between approximately 35 AWGand 45 AWG. In one embodiment, secondary coil 50 has 1000 turns andprimary coil 44 has 26 turns, producing a turns ratio of approximately38:1. In this embodiment, the inductance of secondary coil 50 isapproximately 0.155 H, its resistance is approximately 118 ohms, and itsthickness is approximately 41 AWG. The inductance of primary coil 44 isapproximately between 100 μH and 150 μH, its resistance is approximatelybetween 0.10 ohms and 0.15 ohms, and its thickness is approximatelybetween 20 AWG and 30 AWG.

[0025] Switching device 34, functioning as a transformer drivecircuitry, includes a pulse generator 56, a current limiting resistor58, and transistors 60 and 62. Pulse generator 56 produces a continuousseries of pulses, each of which momentarily allows current to flowthrough transistors 60 and 62. Between the pulses, however, transistors60 and 62 prevent current from flowing from second terminal 48 ofprimary coil 44 to electrical ground. The series of pulses produced byswitching device 34 serves to continuously and cyclically connect anddisconnect second terminal 48 with ground. This, in turn, causes thevoltage of DC power supply 28 to be cyclically applied across andremoved from terminals 46 and 48, thereby producing an alternatingcurrent voltage waveform. Thus, the combination of switching device 34and DC power supply 28 forms a source of alternating current voltagethat is applied across terminals 46 and 48 of primary coil 44. In oneembodiment, pulse generator 56 cycles with a period of approximatelybetween 6 and 8 milliseconds, with a pulse width of approximately 200μs.

[0026] Charging capacitor 30 is charged by DC power supply 28 betweenthe pulses produced by pulse generator 56. During a pulse, however, whencurrent from DC power supply 28 flows through primary coil 44, capacitor30 also discharges through primary coil 44. Thus, capacitor 30 serves toincrease the current sourcing capacity of the source of alternatingcurrent voltage formed by battery 28 and switching device 34.

[0027] Transient voltage suppressor 36 interconnects second terminal 48of primary coil 44 with ground when the voltage at second terminal 48exceeds a predetermined level, such as, for example, 50V. That is,transient voltage suppressor 36 clamps or limits the voltage at secondterminal 48 by draining current from second terminal 48 to ground untilthe voltage at second terminal 48 is again below the threshold voltage,at which transient voltage suppressor 36 prevents further current flowto ground. In this way, transient voltage suppressor 36 functions as avoltage limiting device.

[0028] During operation, transformer 32 acts as a flyback transformerhaving a first mode and a second mode, also known as a flyback mode. Thefirst mode occurs while a pulse is being generated, which causes secondterminal 48 to be connected to ground through transistors 60 and 62. Ina standard flyback transformer circuit implementation, the output of thetransformer is diode rectified, thereby preventing current from flowingin the secondary winding during the first mode. In the presentinvention, however, the output diode is eliminated, thereby allowingtransformer 32 to supply an output across secondary coil 50 during thefirst mode of operation. Transformer 32 operates in a standard step upmanner and the output voltage across secondary coil 50 is a function ofthe DC input voltage, the turns ratio of transformer 32, and the loadapplied to the output terminals 52 and 54.

[0029] The flyback mode occurs between pulses, during which time secondterminal 48 is disconnected from ground. During the flyback mode, theenergy stored in the transformer core or primary coil 44 is transferredto secondary coil 50. The output voltage across secondary coil 50 is afunction of the energy stored in primary coil 44 and the turns ratio oftransformer 32.

[0030] The low output impedance of transformer 32 coupled with theproduction of an output voltage in either of the two modes of operationenables an adequate electroshock stimulus to be applied to the dog ineither a wet or dry environment. In a wet environment, the primaryelectroshock stimulus results from the first operational mode. The loadimpedance applied to the transformer output in a wet environment is verylow in comparison to the skin loading in a dry environment due to theloading effects of the water. Since the primary energy in the firstoperational mode is derived from the input power sources 28 and 30rather than from energy stored in the transformer core, transformer 32is capable of delivering substantially more output power in the firstmode. The low output impedance of transformer 32 is required toeffectively deliver this power to a load which includes the parallelcombination of the water and the animal's skin.

[0031] During the first operational mode, and under a wet, loadedcondition, the output voltage across secondary coil 50 remainsrelatively low (approximately 70V), but the current is relatively high(greater than 100 mA). The power delivered is high enough that, withelectrodes 16 and 18 under water, the shock can be felt by the skinwithout direct electrode contact, and is greatly enhanced with directelectrode contact. During the flyback mode, the available energy islimited to that stored in the transformer core, and the secondary outputpower is much less (less than 50V at less than 100 mA in water).

[0032] In a dry environment, the primary electroshock stimulus resultsfrom the second operational mode when transformer 32 is in a flybackmode. When the skin is dry, the resistance of the skin is relativelyhigh and the higher voltage of the flyback mode is necessary to achievean adequate electroshock stimulus to the skin.

[0033] By voltage limiting device 36 limiting the voltage at secondterminal 48 of primary coil 44, the open circuit output voltage acrossterminals 52 and 54 of secondary coil 50 is also limited. The flybackvoltage present across secondary winding 50 is related to the flybackvoltage generated across primary winding 44 by the turns ratio oftransformer 32. The accuracy of the relationship is affected by thecoupling coefficient, which is a function of the design andmanufacturing processes of the transformer. If the primary to secondarycoupling is adequate, the output voltage amplitude can be limited byclamping the primary flyback voltage at terminal 48 to a thresholdvoltage or clamping voltage. Clamping the primary voltage limits theoutput voltage to approximately the product of the turns ratio and theclamping voltage.

[0034] The clamping voltage is selected so that when the output oftransformer 32 is loaded, i.e., electrodes 16 and 18 are contacting theanimal's skin, the primary voltage is below the clamping voltage and noclamping action occurs. The benefits of voltage clamping device 36 arerealized, however, when no load is applied to secondary coil 50, i.e.,there is no conductive path between electrodes 16 and 18 and thetransformer output voltage is at its maximum (up to 10,000 volts). Thebenefits include allowing closer spacing between the circuitry andcomponents and the high voltage outputs without risking arcing betweenthese parts. Clamping device 36 also allows the use of smaller, lowercost transformer components. With the output voltage clamped to a lowervoltage, the dielectric spacing and potential for internal arcing aresubstantially reduced. This allows the transformer manufacturer toreduce the size of the transformer and eliminate costly manufacturingtechniques to prevent internal arcing. Further, clamping device 36allows the use of lower breakdown voltage transistors in the transformerdriver circuit. This, in turn, allows the use of lower cost and highergain transistors, thereby minimizing the number of transistor gainstages necessary to switch the high primary currents present in highpower flyback transformer designs. Finally, voltage clamping device 36performs a transformer driver snubber function to prevent damage to thedrive transistor circuitry from high peak primary voltages due to thetransformer primary winding leakage inductance.

[0035] In the embodiment shown, voltage limiting device 36 is shown inthe form of a transient voltage suppression diode, also known as atransorb. However, it is to be understood that other types of componentscan also be used as a voltage limiting device, such as a zener diode,for example. Further, instead of using a dedicated voltage limitingdevice, it is also possible to use the breakdown voltages of transistors60 and 62, or the breakdown voltage of a field effect transistor, toclamp the primary voltage at terminal 48. Instead of placing device 36between terminal 48 and ground, it is also possible to connect clampingdevice 36 in parallel with primary coil 44.

[0036] Upon receiving transmitted signal 24, receiver circuit 22activates shock device 26 via a line 42 connected to power supply 28,thereby allowing the voltage to be applied across electrodes 16 and 18.The details of how receiver circuit 22 activates shock device 26 are notgiven in detail herein, as it is also possible for receiver circuit tocontrol pulse generator 56, or to control a switch which may beconnected in series with any of transformer terminals 46, 48, 52 or 54.

[0037] While this invention has been described as having a preferreddesign, the present invention can be further modified within the spiritand scope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. A remote receiver unit for use in an animalbehavior modification system that applies an electrical shock to ananimal, said remote receiver unit comprising: an electrical shock deviceincluding: two electrodes configured for contacting the animal; a sourceof alternating current voltage; and an electrical transformer having aprimary coil and a secondary coil, said primary coil electricallyconnected to said source of alternating current voltage, said secondarycoil electrically connected to at least one of said two electrodes, saidtransformer having an output impedance of less than 900 ohms; and areceiver circuit electrically connected to said shock device, saidreceiver circuit being configured for activating said shock devicedependent upon a received signal.
 2. A remote receiver unit for use inan animal behavior modification system that applies an electrical shockto an animal, said remote receiver unit comprising: an electrical shockdevice including: two electrodes configured for contacting the animal; asource of alternating current voltage; and an electrical transformerhaving a primary coil and a secondary coil, said primary coilelectrically connected to said source of alternating current voltage,said secondary coil electrically connected to at least one of said twoelectrodes, said transformer having an output impedance of less than 800ohms; and a receiver circuit electrically connected to said shockdevice, said receiver circuit being configured for activating said shockdevice dependent upon a received signal.
 3. A remote receiver unit foruse in an animal behavior modification system that applies an electricalshock to an animal, said remote receiver unit comprising: an electricalshock device including: two electrodes configured for contacting theanimal; a source of alternating current voltage; and an electricaltransformer having a primary coil and a secondary coil, said primarycoil electrically connected to said source of alternating currentvoltage, said secondary coil electrically connected to at least one ofsaid two electrodes, said transformer having an output impedance of lessthan 700 ohms; and a receiver circuit electrically connected to saidshock device, said receiver circuit being configured for activating saidshock device dependent upon a received signal.
 4. The remote receiverunit of claim 3 , wherein said output impedance of said transformer isless than 600 ohms.
 5. The remote receiver unit of claim 3 , whereinsaid output impedance of said transformer is less than 500 ohms.
 6. Theremote receiver unit of claim 3 , wherein said output impedance of saidtransformer is less than 400 ohms.
 7. The remote receiver unit of claim3 , wherein said output impedance of said transformer is less than 300ohms.
 8. The remote receiver unit of claim 7 , wherein said primary coilof said transformer includes a first terminal and a second terminal,said source of alternating electrical current comprising: a directcurrent voltage battery including a positive terminal electricallyconnected to said first terminal of said primary coil; and a switchingdevice configured for intermittently interconnecting said secondterminal of said primary coil with electrical ground.
 9. The remotereceiver unit of claim 8 , wherein said source of alternating currentincludes a charging capacitor connected in parallel with said battery,said charging capacitor being configured for increasing a currentcapacity of said source of alternating current.
 10. The remote receiverunit of claim 7 , wherein said primary coil has a first number of turns,said secondary coil having a second number of turns, a ratio of saidsecond number of turns to said first number of turns being approximatelybetween 30 and
 50. 11. The remote receiver unit of claim 7 , whereinsaid secondary coil has a resistance of approximately between 50 and 300ohms and an inductance of approximately between 50 and 300 millihenries.12. The remote receiver unit of claim 11 , wherein said secondary coilhas a resistance of approximately between 100 and 150 ohms and aninductance of approximately between 100 and 220 millihenries.
 13. Theremote receiver unit of claim 11 , wherein said secondary coil includesa wire having a thickness approximately between 35 AWG and 45 AWG. 14.The remote receiver unit of claim 7 , further comprising a hermeticallysealed box containing said electrical shock device and said receivercircuit.